[CentOS] Hosed my software RAID/LVM setup somehow

Ross S. W. Walker rwalker at medallion.com
Wed Oct 17 16:23:51 UTC 2007

Kai Schaetzl wrote:
> Luciano Rocha wrote on Wed, 17 Oct 2007 16:08:31 +0100:
> > mount uses /etc/mtab for displaying current mounts, which is invalid
> > when starting the boot. Check /proc/mounts for the correct values.
> > 
> > You can switch to rw with:
> > mount / -o remount,rw
> > 
> > And then you'll be able to change fstab.
> Yeah, this worked, thanks. I'll write that down :-)
> It would be nice if the system would ignore the problems with 
> md2 and md3 and 
> boot nevertheless as in this case it would have been harmless.
> > the b option to init/boot boots in emergency mode.
> If needed, where would I do that? Can I do an init -b 3 in 
> the repair shell or 
> where would I do this?
> > Seems to be OK. What is happening is that you're telling 
> the system to
> > check the filesystems that where in the MDs in fstab. As 
> there's none
> > (it's lvm now), the boot process complains and drops you to a shell.
> Indeed. I thought that using LVM manager would make the 
> necessary changes 
> (whatever they were) for me. I always avoided LVM as much as 
> I could until 
> recently and when I used it I did that already during 
> installation. This was 
> the first time I changed this stuff on a running system. I 
> learned something 
> today :-) I added the /dev/mapper entries as mounts to fstab 
> now and remounted 
> all and everything is well. Thanks for the quick help!
> I have a small question, though: one of the LVM partitions is 
> used for a 
> (non-active) Xen VM and I cannot mount that as ext3. I know I 
> have to unmount 
> before I can run the VM on it. I want to have a look in it. 
> Is there a way to 
> mount it? xdva isn't recognized as a filesystem.

The LVM has a nested MBR, you will need to use a loopback
specifying the offset of the partition within to get it to
mount properly.

For example:

# fdisk -l -u /dev/es_storage/exch_data.1

Disk /dev/es_storage/exch_data.1: 218.2 GB, 218233831424 bytes
255 heads, 63 sectors/track, 26532 cylinders, total 426237952 sectors
Units = sectors of 1 * 512 = 512 bytes

                       Device Boot      Start         End      Blocks   Id  System
/dev/es_storage/exch_data.1p1             128   426220514   213110193+   7  HPFS/NTFS
# mount -t ntfs -o loop,offset=128 /dev/es_storage/exch_data.1 /mnt


This e-mail, and any attachments thereto, is intended only for use by
the addressee(s) named herein and may contain legally privileged
and/or confidential information. If you are not the intended recipient
of this e-mail, you are hereby notified that any dissemination,
distribution or copying of this e-mail, and any attachments thereto,
is strictly prohibited. If you have received this e-mail in error,
please immediately notify the sender and permanently delete the
original and any copy or printout thereof.

More information about the CentOS mailing list